§ 1066.635 NMOG determination.
For vehicles subject to an NMOG standard, determine NMOG as described in paragraph (a) of this section. Except as specified in the standard-setting part, you may alternatively calculate NMOG results based on measured NMHC emissions as described in paragraphs (c) through (f) of this section.
(a) Determine NMOG by independently measuring alcohols and carbonyls as described in 40 CFR 1065.805 and 1065.845. Use good engineering judgment to determine which alcohols and carbonyls you need to measure. This would typically require you to measure all alcohols and carbonyls that you expect to contribute 1% or more of total NMOG. Calculate the mass of NMOG in the exhaust, mNMOG, with the following equation, using density values specified in § 1066.1005(f):
Where:
mNMHC = the mass of NMHC and all oxygenated hydrocarbon (OHC) in the exhaust, as determined using Eq. 1066.605–2. Calculate NMHC mass based on ρNMHC.
rNMHC = the effective C1-equivalent density of NMHC as specified in § 1066.1005(f).
mOHCi = the mass of oxygenated species i in the exhaust calculated using Eq. 1066.605–2.
rOCHi = the C1-equivalent density of oxygenated species i.
RFOHCi[THC-FID] = the response factor of a THC-FID to oxygenated species i relative to propane on a C1-equivalent basis as determined in 40 CFR 1065.845.